"Bumpy" basement walls

[Galten]

My basement walls were full of holes from old plumbing and in some rooms, there was significant plaster peeling. Now I have filled in with gypsum mortar and then puttied with regular sand putty to create smooth surfaces.

But now I have a mix of smooth surfaces and "bumpy" old plaster that doesn't look very nice. How do you make a bumpy surface on the smooth parts?

 

[GoC]

Common filler and a slightly harder round brush to "sculpt" something resembling the rest of the wall.
Slap on filler and let loose with your artistic talents.

 

[Galten]

Thank you!